YEP the voiced segment covers the Alternate Diego summoning his version of The World and whatnot, and while it was difficult to tell at first, it became clear as he went on that it was Koyasu voicing him, and in a way distinctly different from how he voices PBDio and SCDio, which are even distinctly different from one another as well.

If David Production does part 3, I'll be more than happy, BUT from what I understand, they lost a lot of potential budget for it on Hyperdimension Neptunia (really, guys, did you seriously expect an obscure fanservice anime to make any money) so the rebroadcast will hopefully drive up DVD/Bluray sales and THEN we can have Stardust Crusaders.